stl pair

// make_pair example
#include <utility>      // std::pair
#include <iostream>     // std::cout

int main () {
  std::pair <int,int> foo;
  std::pair <int,int> bar;

  foo = std::make_pair (10,20);
  bar = std::make_pair (10.5,'A'); // ok: implicit conversion from pair<double,char>

  std::cout << "foo: " << foo.first << ", " << foo.second << '\n';
  std::cout << "bar: " << bar.first << ", " << bar.second << '\n';

  return 0;
}

make_pair

pair.first

pair.second

 

 

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Sorting a vector of pairs:

sort(changes.begin(), changes.end(), pairCompare);

在pairCompare函数中定义比较方法：

static bool pairCompare(const pair<int, int> pa, const pair<int, int> pb){
        return pa.first<pb.first;
    }

 

before sorting
2	10
9	-10
3	15
7	-15
5	12
12	-12
15	10
20	-10
19	8
24	-8
after sorting
2	10
3	15
5	12
7	-15
9	-10
12	-12
15	10
19	8
20	-10
24	-8